Improvement in separating silver and gold from lead



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Separating Silver and Gold from Lead.`

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Patened Feb. 10,181741.

UNITED STATES PATENT EEICE.

DAVID l. VEBSTER, CHARLES C. LEXVIS, AND ALMAR I). VEBSTER, OF NEWTvonk,

IMPROVEMENT IN `SEPARATING SILVER AND GOLD FROM LEAD.

Specification forming part of Letters Patent No. 147,454, dated February10, 1R74 application tihd January 9, 1874.

. CHARLES C. LEwrs, and ALMAR I. WEBSTER,

of the city, county, and Stat-e of N ew York, have made certain new anduseful Improve Vments in the Arts of Extracting Silver and Gold fromLead, which have not been used or known previous to our invention.

By our improvement, we are enabled to effectually desilver the sameweight of metal in one-third less time, and at one-third less expense,than has heretofore been employed for the same purpose.

The following, with the accompanying drawings, is a full and exactdescription of the apparatus and process employed and practiced by us,which will enable others skilled in the arts of separa-ting silver andgold from lead to practice it.

Figure lis a double furnace having three kettles. The upper two kettlesare thirty-three inches in diameter each, and eighteen inches in depth,made of castiron a half-inch in thickness, holding each two tons ofmelted metal. The lower kettle isforty-iive inches in diameter andtwenty-four inches in depth. The furnaces are constructed of brick, witha cover of cast-iron, formed of two sections, each with a iiange of fourinches projection for holding or binding the brick. The kettles haveflanges about four inches in width, which rest on the cast-iron topplate, and thus form a tight'connection. At the right of the largerpart, hav ing the two kettles, is a door, h, opening to the iire-boX,which reaches beyond the two kettles, and to a flue for carrying offsmoke to the stack. At the left of the lower part, having one kettle, isa pit, e, for access to the door and nre-box of this part, for heating1the kettle. This lower and larger kettle has the capacity for holding`four tons of melted metal.

Fig. 2 is an iron-plate disk a quarter-inch thick, and of diametercorresponding to the interior of the two upper kettlcs. This disk isperforated'by many holes.

The above constitute the apparatus for carrying on the first part of theprocess.

Figs. 3, 4, and 5 represent the apparatus employed for the second partof the process.

Fig. 3 is a longitudinal section. of the furnace, showing theretort aand the angle at which it is set. .'.lhe arch d, Figs. 3 and 4, servesto shield the retort from the direct action of the iiame. The smalliiues h h admit the flame and heat above the arch, and are located atthe fourcorners ofthe furnace. The iire-box is indicated byf in bothfigures, and the ash-pit by g.

The retort is made, preferably, of east-iron, in the shape of a bottle,having attached to and cast with it, at its bottom, two pipes, as shownat b b, Fig. 3. The body of the retort is cylindrical, two feet diameteroutside, and two feet nine inches long between the points where thecontraction is commenced. The mouth or neck is nineteen inches long andeleven in diameter. are fourteen inches long each, and four and one-halfoutside diameter, making the whole length Iivc and one-half feet. Theuniform thickness of the metal is one inch.

Fig. 4 is a cross-section of the furnace, in which the arch is moreplainly shown at l than it is in Fig. 3. The furnace is built offire-brick, stayed and braced by iron bands and rods, as is usual in theconstruction of like furnaces.

Figisa perspective view of the furnace, showing the mouth end of theretort and part of the kettle at the opposite end c, for collecting themelted metal when allowed to run from the retort. The outside dimensionsof this furnace are ve feet ten inches long, five feet wide, and fourfeet ten inches high. The walls are nine inches thick. The retort withinthe furnace rests upon piers of tire-brick built upon the arch. The twonecks or pipes at the lower end of the retort are provided so that, whenthe one on the side placed nearest the iire becomes defective, it may beturned uppermost, and thus the retort is made to last much longer thanif only one pipe were provided. '.lhe upper pipe is always kept closed.

The first step in the process for extracting the silver or gold fromlead is practiced as follows: For example, if the lead to be operatedupon contains two hundred ounces of silver to the ton, we put twohundred and forty `pounds metallic zinc in the bottom of each of theupper kettles a a, Fig. l. Over each of these we The pipes at the bottomf ing this time the metal is heated considerably above the degree of itsmelting temperature,r and stirred during forty-five minutes.

dross is next skimmed oi' at intervals of aboutk The ten minutes, duringan hour longer, when the lead is drawn off by withdrawing an iron plug,b b, by means of a screw and iron rod passing to the bottom of thekettle through the melted metal. It is collected in the lower kettle,and from this cast into pigs. The dross thus formed and now containingthe silver and zinc with some lead, is put into the retort (a, Fig. 3,)and melted. The lead is drawn oii' at the small pipe b to the'kettle Cthen, after stopping` the pipe, one thousand pounds of bullion or lead4containing silveris passed into the retort with neck ormouth of theretort should be kept closed by inserting` the bottom of a plumbagocrucible into it as much as practicable, iny order to excludeatmospheric air. f 1u the kettle C, now free from silver, is

The lead cast into pigs. The rich dross containing the silver remainingin the retort is next removed and placed on an iron plate, and while hotit is granulated. The granulated dross is next put into bottle-shapedplumbago retorts arranged in suitable furnaces, and the zinc distilledand collected in the manner de'- scribed in technical works relating tothe metallurgy of zinc. lead leftin the plumbago retorts is next castinto ingots, and finally yplaced on the cupel in the cupel-furnace andthere relined.

We would here remark that we prefer a cylindrical retort, as describedand represented in Fig. 3, for obvious reasons; but other forms might beused, provided such were constructed with a small mouth, which could bereadily kept closed, so as to exclude the access of air during thegreater time of the treatment.

Having described the process involving our improvements, whatwe claim asof our invention, and desire to secure by Letters Patent of the UnitedStates, is f 1. The perforated iron disk for holding the zinc to theybottom of the kettle until the lead is melted, and then causing it tobe distributed through the metal above, so as to come in contact withand take up the alloyed silver. y

2. The combination of furnaceand inclined retort, substantially asdescribed, and for the purpose set forth. j

k3. The treatment of the skimmings or dross in a closed retort,substantially as described.

4. The treatment of the silver dross in a f chamber in which the air isso highly rareed that it has little or no oxidizing etfect upon thezinc, substantially as described.

5. The concentrating of leadk dross containing silver, derived fromtreatment of lead by any of the usual processes, in a closed retort orchamber from which the air is excluded, substantially in the mannerdescribed.

DAVID P. WEBSTER. CHARLES C. LEWIS. ALMAR I. WEBSTER.

In presence of- J. O. NoxoN, l). D. PARMELEE.

The silver and remaining

